A variety of climbing rungs for anchoring to wall surfaces have been proposed employing a generally U-shaped rung consisting of two parallel legs for anchoring into a wall and spaced apart by a central element or tread.
For example in Canadian Letters Pat. No. 716,881 (corresponding U.S. Pat. No. No. 3,374,532) I disclosed a process for making a rung whereby a flexible, synthetic plastics material sleeve is fitted over a straight length of metal tubing and the length of metal tubing sheathed in plastic is bent into a U-shape to form a climbing rung. Such a bending serves to stretch the plastics material sleeve so that it grips the metal tubing. The anchoring legs may then be permanently inserted into receptive bore holes in a wall.
In Canadian Letters Pat. No. 936,845 I dealt with the risk of oxidation and rusting of the anchoring legs of a rung which are embedded in a wall. According to the invention disclosed a steel tube is bent into a U-shape to form a climbing rung and is covered with a non-corroding coating, for example of aluminium or plastics material. Both ends of the tubular rung are plugged. For each climbing rung two anchor sleeves corresponding to the ends of the rung are provided which are adapted to be located in suitably placed bore holes in a wall. The anchor sleeves, made from plastic or nylon are in the shape of a tubular shell having a slightly conical inner bore and are sealed at one end. When the ends of the rung are forced into the slightly conical inner bore of the anchor sleeve located in the bore holes in a wall, the anchor sleeve expands and is jammed very tightly into the bore hole.
The exposure of the ends of the rung to oxidation, rusting and corrosion is thereby mitigated. However, a tight seal at the overlap of the protective coating for the steel tube, such as the end of a jacket sleeve, with the respective anchor sleeve is not always ensured. In particular, use of the rung will result in flexion and vibration spreading corrosion materials between the anchor sleeve, protective jacket and steel tube advancing corrosion of the steel tube. This corrosion is not visible to inspection. In addition, water and corrosive materials may penetrate into the space between the outside surface of the sleeve and the bore hole, subjecting the bore hole which comprises the portion of the wall surrounding the anchor sleeve to chemical disintegration.
One solution to the problem of water and corrosive substances penetrating the spaces between the anchor sleeve, protective jacket and steel tube has been to bend a climbing rung, made of steel tubing or steel reinforcing rod to the desired configuration and then to encapsulate it in a corrosion resistant material such as recovered battery case material by means of an injection moulding process. The protective jacket thereby surrounds the preformed inner reinforcement effectively sealing it against corrosion. The ends of this type of step comprising anchoring projections may be driven directly into bore holes in a wall. However, the bore hole is still subject to penetration by water or corrosive substances.
It is therefore an object of this invention to provide an improved anchor and climbing rung which may be anchored in a wall without thereby exposing the wall at the anchoring site to permeation or penetration by water or corrosive substances.
Further and other objects of the invention will be apparent to those skilled in the art from the following summary of the invention and detailed description of preferred embodiments thereof.